You don't know because you haven't read the entire Quran carefully.
Solomon's army consisted not only of humans, but also of jinn and birds.
Prophet Solomon is in communication with birds, jinns and even mountains. In other words, nature/all living things know it closely. The name/fame of himself and his army was in the language of all animals at that time.
By the way, the Qur'an states that all living things, with the exception of some people, constantly remember Allah.
In short, if we decipher the language of insects, animals and all nature with technology, you will see that they know a lot. Especially they know much more than you.